Systems and Methods for Separating Yttrium and Strontium

ABSTRACT

Systems and methods for separating Y and Sr are provided. The systems and methods provide combinations of solutions, vessels, and/or media that can provide Y solutions of industrially beneficial concentration.

STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY-SPONSOREDRESEARCH AND DEVELOPMENT

This invention was made with Government support under ContractDE-AC05-76RL01830 awarded by the U.S. Department of Energy. TheGovernment has certain rights in the invention.

TECHNICAL FIELD

The present disclosure relates to the separation of yttrium andstrontium, and in particular embodiments, the present disclosure relatesto the separation of yttrium and strontium isotopes and/or thepreparation of concentrated forms of yttrium isotopes.

BACKGROUND

Yttrium isotopes typically can be fission products along with strontiumisotopes and exist in the same solution as strontium isotopes. Thesefission products are generated by fissioning of actinides. Sr cyclotrontargets can produce other isotopes by (p, n) reactions. The presentdisclosure provides systems and methods for separating yttrium fromstrontium, isolating yttrium isotopes from a solution of strontium andyttrium isotopes, and/or the preparation of concentrated forms ofyttrium isotopes.

SUMMARY OF THE DISCLOSURE

Methods are provided for separating yttrium (Y) and strontium (Sr). Themethods can include providing a dilute acidic mixture that includes Yand Sr to a vessel having a media therein. The methods can furtherinclude while providing the dilute acidic mixture, retaining at leastsome of Y from the dilute acidic mixture within the first vessel whileat least eluting some of the Sr from the dilute acidic mixture to form adilute acidic eluent.

Additional methods for separating Y and Sr are provided that can includeproviding a vessel containing a media and a dilute acidic mixturecomprising Y. The methods can include providing a concentrated acidmixture to the vessel and while providing a concentrated acid mixture tothe vessel recovering a concentrated acid eluent comprising at leastsome of the Y from within the vessel.

Additional methods for separating Y and Sr are also provided that caninclude providing a concentrated acidic mixture comprising Y to a vesselhaving a media therein and while providing that concentrated acidicmixture retaining at least some of the Y from the concentrated acidicmixture within the vessel and forming an eluent.

Further methods are also provided that can include methods forseparating Y and Sr. The methods can include providing a vesselcontaining a media and a concentrated acid mixture that includes Y. Themethods can include providing a dilute acid mixture to within the vesseland while providing a dilute acidic mixture to within the vesselrecovering a dilute acid eluent that includes at least some of the Yfrom within the vessel.

Additional methods for separating Y and Sr are also provided that caninclude providing a first mixture comprising Y and Sr to a first vesselhaving a first media therein. The methods can include retaining at leastsome of the Y from the first mixture within the first vessel andproviding a second mixture to the first vessel. The methods can furtherinclude recovering a first eluent comprising at least some of the Y fromwithin the first vessel and providing the first elute that includes Y toa second vessel having a second media therein. The methods can alsoinclude retaining at least some of the Y from the first eluent withinthe second vessel and providing a third mixture to the second vessel.The method can also include recovering a second eluent that includes atleast some of the Y from within the first vessel.

Methods for separating Y and Sr can also include providing a firstmixture of at least two components to a first vessel having a firstmedia therein with the first vessel defining a first volume. The methodcan include retaining at least some of one of the two components withinthe first vessel and eluting the one of the two components from thefirst vessel to a second vessel having a second media therein. Thesecond vessel can define a second volume and the first volume can begreater than the second volume. The first media can be different fromthe second media. The methods can include retaining at least some of theone of the two components within the second vessel and eluting the oneof the two components from the second vessel. Additionally, the elutionfrom the first vessel can have a first concentration of the onecomponent and with the elution from the second vessel can have a secondconcentration of the one component. The second concentration can begreater than the first concentration.

DRAWINGS

FIG. 1 is system for practicing methods according to an embodiment ofthe disclosure.

FIG. 2 is a system for practicing methods according to an embodiment ofthe disclosure.

FIG. 3. is distribution coefficient data in accordance with embodimentsof the present disclosure.

FIG. 4 is a system for practicing methods according to an embodiment ofthe disclosure.

FIG. 5 is a system for practicing methods according to an embodiment ofthe disclosure.

FIG. 6 is a system for practicing methods according to an embodiment ofthe disclosure.

FIG. 7 is data acquired utilizing systems and methods according to anembodiment of the disclosure.

FIG. 8 is data acquired utilizing systems and methods according to anembodiment of the disclosure.

FIG. 9 is data acquired utilizing systems and methods according to anembodiment of the disclosure.

FIG. 10 is data acquired utilizing systems and methods according to anembodiment of the disclosure.

FIG. 11 is data acquired utilizing systems and methods according to anembodiment of the disclosure.

FIG. 12 is data acquired utilizing systems and methods according to anembodiment of the disclosure.

FIG. 13 is data acquired utilizing systems and methods according to anembodiment of the disclosure.

FIG. 14 is data acquired utilizing systems and methods according to anembodiment of the disclosure.

FIG. 15 is data acquired utilizing systems and methods according to anembodiment of the disclosure.

FIG. 16 is data acquired utilizing systems and methods according to anembodiment of the disclosure.

FIG. 17 is data acquired utilizing systems and methods according to anembodiment of the disclosure.

FIG. 18 is data acquired utilizing systems and methods according to anembodiment of the disclosure.

FIG. 19 is data acquired utilizing systems and methods according to anembodiment of the disclosure.

DESCRIPTION

The systems and methods of the present disclosure will be described withreference to FIGS. 1-19. Referring first to FIG. 1 a system 10 isdisclosed that includes at least two vessels 12 and 14 that can be influid communication via conduit 16 as well as another conduit 18. As forall vessels and conduits described in this description they can likewisebe referred to as containers or holders or really any form of apparatusthat can retain liquid or solid particles, and/or mixtures thereofwithin a confined or predefined space. Conduits 16 and 18 arerepresented as continuous here but throughout the specifications shouldbe recognized that they can be valve operable to be opened or closed asdesired to provide or not provide fluid communication between one vesseland another. The conduits can also be configured to provide the solutionthat is being exchanged or provided through them. Therefore, by example,the conduits can be resistant to acid or organic acids or resistant toorganics themselves as needed. In accordance with exampleimplementations the methods for separating Y and Sr can includeproviding a dilute acidic mixture including Y and Sr. This dilute acidicmixture of Y and Sr can be in vessel 12 for example and this diluteacidic mixture can include nuclides of Y (for example ⁹⁰Y, ⁸⁹Y, ⁸⁸Y, or⁸⁶Y) as well as nuclides of Sr (for example ⁹⁰Sr, ⁸⁹Sr, ⁸⁸Sr or ⁸⁶Sr).This dilute acidic mixture can be sourced from Sr-bearing nuclearmaterial stockpiles which can be a biproduct of nuclear processing. Forexample, ⁸⁶Y is a 14.7 hr half-life isotope produced by the (p, n)reaction onto an isotopically enriched ⁸⁶Sr target. In the case of⁸⁶Y/⁸⁶Sr, it can be a result of proton bombardment onto a ⁸⁶Sr cyclotrontarget.

General recipes for the preparation of solutions that can simulateSr-bearing stockpile materials are provided in Table 1.

TABLE 1 General recipe to prepare a ⁹⁰Sr-bearing simulant solutioncontaining Group II elements and Y that approximate those found in anexample ⁹⁰Sr product solution. ⁹⁰Sr simulant Spike conc., Desired conc.,Spike vol., sol'n. Element spike mg/mLb μg/mL μL components Ca 99.26 54033.0 Sr 260.21 50,250 1770 Ba 8.55 20 14.2 Y 3.42 2.30 4.1 Total elementspike vol. = 1.22 ⁹⁰Sr spike vol. = 0 c  0.1M HCl diluent vol. = 4.84Total vol. = 6.06

Spiked solutions can also be prepared with reference to Table 2 below aswell.

TABLE 2 ⁹⁰Sr activities that were spiked into each column load solutionprior to ⁹⁰Y purification. Determined ⁹⁰Sr Run Run date activity μCi^(a, b) 1 Feb. 15, 2019 3.96E+2 (2.12E+0) 2 Feb. 20, 2019 7.41E+2(2.12E+0) 3 Feb. 21, 2019 7.66E+2 (1.56E+0) 4 Feb. 21, 2019 6.82E+2(8.85E−1) 5 Fab. 27, 2019 7.02E+2 (5.05E−1)

In accordance with example implementations acidic reagents can beutilized such as solutions of dilute acidic mixtures and concentratedacidic mixtures prepared with the reagents disclosed below for example.

Concentrated hydrochloric acid (HCl) can be ACS Certified grade orhigher (Fisher Scientific, Waltham, Mass.). Dilutions of HCl can beprepared from deionized water (≥18 MΩcm) using a Barnstead E-Pure waterpurification system (Dubuque, Iowa). Scintillation cocktail wasUltimaGold AB (PerkinElmer, Billerica, Mass.).

A supply of ˜5 mCi ⁹⁰Sr in ˜2% HNO₃ can be obtained and this solutioncan be evaporated to nitrate salt, then transformed to formate salt. The⁹⁰Sr residue can be evaporated and transformed to chloride salt prior touse. An infrared lamp can be used to evaporate metered volumes of thetransformed ⁹⁰Sr stock solution to Teflon vials (7 mL round-bottom vial,Savillex, Eden Prairie, Minn.).

Single element solutions containing concentrates of Ca(II), Sr(II),Ba(II), and Y(III) in 0.1 M HCl can be prepared, as briefly describedbelow:

-   -   Ca solution can be prepared by dissolving calcium metal chips in        concentrated. HCl. After evaporation of excess acid, the CaCl₂        salts can be brought up in 0.1 M HCl. Prepared Ca(II)        conc.=99.26 mg/mL.    -   Sr solution can be prepared from strontium(II) carbonate salt.        The salt can be saturated with conc. HCl to destroy carbonate        and convert the salts to strontium chloride. The excess acid can        be evaporated off overnight, and then the dried salts were        brought up in 0.1 M HCl. Prepared Sr(II) conc.=260.21 mg/mL.    -   Ba solution can be prepared from barium(II) chloride salt. The        salt can be dissolved directly in 0.1 M HCl. Prepared Ba(II)        conc.=8.55 mg/mL.    -   Y solution can be prepared from yttrium(III) chloride salt. The        salt can be dissolved directly in 0.1 M HCl. Prepared Y(III)        conc.=3.42 mg/mL.

Aliquots of these solutions can be added to ⁹⁰Sr-spiked solutions inorder to simulate the dissolved solids present in ⁹⁰Sr stocks.

In accordance with example implementations, and with reference to FIG.1, this dilute acidic mixture can include Y and Sr can be provided tovessel 14 having a first media 20 therein. The dilute acidic mixture canhave a pH less than 7 and the dilute acidic mixture can also have a pHless than 3. The dilute acidic mixture can have a concentration of acidthat is less than 0.1M, for example, but must include sufficient acid toremain acidic. As described herein the dilute acidic mixture canadditionally include elemental Sr, Ca and/or Ba and the dilute acidmixture can include stockpiled Sr-bearing nuclear material for example.

Within vessel 14 can be a first media 20 that includes a resin. Thisresin can include Bis(2-ethylhexyl) hydrogen phosphate (HDEHP). Thefirst media can also include alkylphosphorus extractants. Alternatively,the first media can also include Si. In accordance with exampleimplementations the media 20 can be considered a first media.

The Y purification method can employ two columns or vessels in tandem.First vessel 14 can have media 20 that includes aDi-(2-ethylhexyl)phosphoric acid (HDEHP)-based extraction chromatographyresin, sold under the trade name Ln Resin (Eichrom Technologies, Ltd,Lisle, Ill.). The particle size distribution used was 100-150 μm, butother size distributions such as 50-100 μm or 20-50 μm are contemplated.

The Ln Resin can be packed into a column having a ˜0.25 cc internalvolume in a 1 cc SPE tube kit (Supelco) that can be cut to theappropriate dimension. The columns can be polypropylene, with 20 μm poresize polyethylene frits. The column can be fitted with a custom-madeplastic cap (with female luer fitting) that can be inserted into the topof the trimmed column.

In accordance with example implementations, while providing the diluteacid mixture comprising Y and Sr the method can provide for retaining atleast some of the Y from the dilute acidic mixture within vessel 14while eluting some of the Sr from the dilute acidic mixture to form adilute acidic eluent which would be provided to conduit 18. Inaccordance with example implementations the method can also includeproviding the dilute acidic mixture from reservoir 12 and then providingthe dilute acidic eluent to reservoir 12 via conduit 18 for example.

In accordance with example implementations, the dilute acidic mixturecan further comprise Zr and the method can also include while providingthe dilute acidic mixture, retaining at least some of the Zr from thedilute acidic mixture within vessel 14. The method can also includefurther retaining at least some of the Fe from the dilute acidic mixturewithin vessel 14. The dilute acidic mixture can include HCl for example,an organic acid for example, such as formic acid for example.

Referring next to FIG. 2 a system 25 is depicted that can include avessel 14 containing a media 20 and a dilute acidic mixture 22 thatincludes Y. In accordance with example implementations vessel 14 can bethe vessel of system 10 after the providing of the Y/Sr mixture 12 tovessel 14 for example. In accordance with example implementations aconcentrated acid mixture contained in vessel 24 can be provided viaconduit 26 to vessel 14. While providing the concentrated acid mixtureof vessel 24 to vessel 14 an acid eluent comprising at least some of theY from within vessel 14 can be recovered in vessel 30 as eluent 32 viaconduit 28.

In accordance with example implementations, vessel 14 can include one orboth of Zr and Fe and while providing the concentrated acid mixture fromvessel 24 to vessel 14 at least some or both of the Zr and Fe can beretained. In accordance with example implementations this concentratedacid mixture can include HCl, an organic acid, such as formic acid forexample. In further embodiments the method can provide the concentratedacid eluent of 32 from within vessel 30 to another vessel containinganother medium. This additional embodiment will be described with moredetail herein. Additionally the media 20 remains as the media 20 asdescribed in system 10 for example.

In accordance with an example embodiment, tandem column-based ⁹⁰Ypurification methods are contemplated and described herein. Referring toFIG. 3, the affinity for Y on Ln Resin drops approximately as a negativepower function with increasing HCl concentration. At 0.1 M HCl, thedistribution coefficient (K_(d)) for Y exceeds 105 mL/g; by the time HClconcentration has increased to 8 M HCl, Y K_(d) drops by ˜6 orders ofmagnitude. This substantial change in Y affinity between the two HClconcentrations can dictate what is considered a dilute acidic orconcentrated acidic mixture. In accordance with example implementationsand with respect to the systems and methods of the present disclosure, adilute acidic mixture, for example, can be an acid mixture that providesfor a K_(d) of at least 10, while a concentrated acidic mixture, forexample, can provide for a K_(d) of less than 10; each of which withregard to Y on a HDEHP resin such as Ln Resin.

Further, with reference to FIG. 3, Zirconium-90 is a contaminant ofconcern in aged ⁹⁰Sr-bearing stockpiles, as it is the stable decayproduct of ⁹⁰Y. Therefore, it accumulates in the ⁹⁰Sr stocks over time.The data in FIG. 3 demonstrates that Zr(IV) affinity for Ln Resin is>10⁴ mL/g across the entire range of HCl concentration. Therefore, aprimary Ln Resin column is capable of ⁹⁰Zr removal during the ⁹⁰Y loadstep. Furthermore, ⁹⁰Zr is retained on the column while ⁹⁰Y is elutedand may pass to column 2 (see Table 3).

FIG. 3 also provides a K_(d) map for Fe(III) on the first media such asLn Resin. During the column 1 load step (0.1 M HCl), Fe may have a K_(d)of ˜10³ mL/g. Accordingly, most, if not all, of this contaminant can beretained on column 1 during the ⁹⁰Y load/wash (i.e., the Y/Sr diluteacid mixture is provided to the first vessel). Additionally, Fe can havea K_(d) of ˜1300 mL/g at 8 M HCl. Accordingly, Fe can be retained on thecolumn during the ⁹⁰Y transfer step (see Table 3 below, and inaccordance with system 25).

TABLE 3 Example behavior of Y(III) and Sr(II) through the tandem columnprocess. While not exclusively evaluated during the present study, thebehavior of Fe(III) and Zr(VI) are also shown. Active Conc. HCl,Retained (↑) or unretained (↓) Step Description column moles/L Y(III)Sr(II) Zr(IV) Fe(III) 3 ⁹⁰Y load/wash C1 0.1 ↑ ↓ ↑ ↑ 4 ⁹⁰Y transfer C1 →C2 8 ↓→↑ ↓→↓ ↑→↑ ↑→↑ 5 Wash C2 8 ↑ ↓ ↑ ↑ 6 ⁹⁰Y elute C2 0.1 ↓ ↓ ↓ ↓

Referring next to FIG. 4 system 35 is provided that includes a vessel 36having a media 38 therein in fluid communication via conduit 44 tovessel 40 having a mixture 42 therein and operatively coupled to anotherconduit 46 for retrieving any eluent from vessel 36. In accordance withexample implementations methods are provided for separating Y and Srthat can include providing a concentrated acid mixture 42 with this acidmixture comprising Y to vessel 36 having media 38 therein. Thisconcentrated acid mixture can be provided from the methods and systemsof FIG. 2 as described herein and vessel 36 can be aligned with system25 for example to receive an acidic eluent therefrom.

In accordance with example implementations media 38 can include a resinsuch as diglycolimide resin, for example (diglycolamide)-basedextraction chromatography resin, sold under the trade name DGA-NormalResin (Eichrom Technologies, Ltd.). The particle size distribution usedcan be 20-50 μm, 50-100 μm, and/or 100-150 μm Example extraction mediacan include N,N,N′,N′-tetra-n-octyldiglycolamide.

The concentrated acid mixture can include at least some of the Sr forexample as radioactive and stable isotopes of Sr such as ⁹⁰Sr, ⁸⁹Sr,⁸⁸Sr, or ⁸⁶Sr. The method can include while providing the concentratedacid mixture retaining at least some of the Y from the concentrated acidmixture within vessel 36 and forming an eluent that can include at leastsome of the Sr in conduit 46. At least some of the concentrated acidmixture can include Zr and the method can include, while providing theconcentrated acid mixture to vessel 36, retaining at least some of theZr from the concentrated acid mixture. Additionally or separately, atleast some of the concentrated acid mixture can include Fe and themethod can include, while providing in the concentrated acid mixture,retaining at least some of the Fe from the concentrated acid mixturewithin vessel 36.

Referring next to FIG. 5 system 50 is provided that can include vessel36 having media 38 therein as well as a concentrated acid mixture 42that includes Y. In accordance with example implementations vessel 54can include a dilute acid mixture 56. This dilute acid mixture can beprovided to within vessel 36. The method can provide for, whileproviding dilute acid mixture 56 to within vessel 36, recovering adilute acid eluent in conduit 52 that can include at least some of the Yfrom within vessel 36. The media within vessel 36 can be as describedwith reference to FIG. 4 for example.

The vessel 36 can include at least some of the Y for example asradioactive and stable isotopes of Y such as of 90Y, ⁸⁹Y, ⁸⁸Y, or ⁸⁶Y,for example. The vessel can also contain one or more of Zr or Fe and themethod can further include for providing dilute acid mixture 56 tovessel 36 eluting at least some of one or both of Zr and/or Fe withinvessel 36. As described herein the dilute acidic mixture can include HCland the mixture can include an organic acid such as formic acid forexample. Additionally while providing the dilute acid mixture to vessel36, the method can include eluting at least some of the Sr within thevessel.

Referring next and with reference to FIG. 6 a system 60 is providedwherein vessels 14 and 36 are provided in tandem and embodiments of thesystems of 10, 25, 35, and 50 described herein are utilized together toprepare an eluent 52 comprising Y. In accordance with exampleimplementations and with reference to FIG. 6 a first mixture 12 acomprising Y and Sr can be provided to a first vessel 14 having a firstmedia 20 therein. This first mixture can be a dilute acidic solution andthe first media can be an alkylphosphorus extractant resin such as HDEHPresin. At least some of the Y from first mixture 12 a can be retainedwithin vessel 14 utilizing media 20 for example.

In accordance with example implementations a second mixture 24 a can beprovided to first vessel 14 and the method can further includerecovering a first eluent 28 and providing first eluent 28 that includesY to a second vessel 36 having a second media 38 therein. The secondmixture can be a strong acidic or concentrated acidic solution such asHCl and the second media can be a diglycolamide resin such as N, N, N′,N′-tetra-n-octyldiglycolamide. The method can further include retainingat least some of the Y from first eluent 28 within second vessel 36utilizing media 38 for example and providing a third mixture 42 tosecond vessel 36 and, when providing third mixture 42, recovering asecond eluent 52 that includes at least some of the Y from the firstvessel. This third mixture can be a weak or dilute acid mixture such asHCl.

In accordance with other example implementations and with reference toFIG. 6 a first mixture 12 a comprising Y and Sr can be provided to afirst vessel 14 having a first media 20 therein. At least some of the Yfrom first mixture 12 a can be retained within vessel 14 utilizing media20 for example. In accordance with this embodiment the first mixture canbe a strong acidic or concentracted acidic solution such as HCl and thefirst media can be diglycolamide resin such as N, N, N′,N′-tetra-n-octyldiglycolamide.

Continuing with this embodiment, a second mixture 24 a can be providedto first vessel 14 and the method can further include recovering a firsteluent 28 and providing first eluent 28 that includes Y to a secondvessel 36 having a second media 38 therein. This second mixture can be adilute or weak acidic solution that can include HCl and the first mediacan be an alkylphosphorus extractant resin such as HDEHP resin.

The method can further include retaining at least some of the Y fromfirst eluent 28 within second vessel 36 utilizing media 38 for exampleand providing a third mixture 42 to second vessel 36 and, when providingthird mixture 42, recovering a second eluent 52 that includes at leastsome of the Y from the first vessel. This third mixture can be a strongor concentrated acid mixture such as HCl.

Additionally the method can provide that vessels 14 and 36 are ofsubstantially different sizes with vessel 14 being at least as large butcan be larger than vessel 36. In such a configuration, the Y recoveredfrom the systems and methods of the process can be in a concentratedform and suitable for industrial use. Accordingly, the volume of vessel14 can be larger than the volume of vessel 36.

Table 3 above also indicates the behavior of the four selected ions onthe second media (DGA Resin) during the ⁹⁰Y transfer, secondary wash,and ⁹⁰Y elute steps.

An example system schematic 60 is shown in FIG. 6, and the labels aredefined in Table 4 below. System 60 includes three pumps (PP, SP1, andSP2). These pumps are provided as one or more of many potential fluiddelivery systems, that can also include gravity.

TABLE 4 Listing of schematic labels presented in FIG. 6. Label ID LabelID SP1-SP2 Syringe pumps 1 & 2 D In-line ⁹⁰Y product detector (optional)V1 6-port, 2-pos valve FC Fraction collector V2-V3 2-port, 2-pos. valvesSR Sample reservoir PP Peristaltic pump ⁹⁰Sr/Y L Load line for ⁹⁰Sr/Y C1Ln Resin column ⁹⁰Sr R ⁹⁰Sr return line C2 DGA column OF ⁹⁰Sr/Y overflowline SL Sample injection loop

System 60 can be programmed to perform the series of steps outlined inTable 5 below. Delivered reagent volumes and flow rates through thecolumns may be set, as described below.

The reagent volumes programmed to be delivered to system 60 can be afunction of the fluid delivery systems displacement volume, for examplewherein one (or two) syringe volumes were delivered for a particularstep. The delivered volumes can be deliberately programmed to beexcessive (i.e., many bed volumes of reagent delivered through thecolumns).

TABLE 5 Tandem column ⁹⁰Y purification method steps as tested. ActiveConc. HCl, Delivered vol., Flow rate, Step Description column moles/L mL^(a) mL/min ^(a) Footnotes 1 Condition C1 C1 0.1 3  1-2 2 Condition C2C2 8 2 0.5-1 3 ⁹⁰Y load/wash C1 0.1 20  1-2 b. 4 ⁹⁰Y transfer C1 → C2 810 0.5-1 5 Wash C2 8 2.5 0.5-1 6 ⁹⁰Y elute C2 0.1 2.5  0.2-0.5 c. 7Clean-up All H₂O 1-3 0.5-2 d. ^(a) As tested; other concentrations,amounts delivered, and/or flow rates are contemplated. b. ⁹⁰Srunretained; the ⁹⁰Y-depleted load/wash solution was returned to areservoir for eventual reuse. c. The bulk of the ⁹⁰Y product is in thefirst ~0.5 to ~0.7 mL elute fraction. d. Water was flushed through allfluid transport lines and then the lines were purged with air. Thisincluded a water flush through the SL using thePP.

The flow rates may be ultimately limited by a number of factors, whichmay include the following: the back-pressure generated by the fluidpathways (primarily the columns); the amount of back-pressure thecolumns or fittings or pumps can handle prior to leaking; the amount ofback-pressure the extraction chromatography resin can handle prior tobleeding excessive extractant; and the adsorption/desorption rate of theanalytes on the column resins. The flow rate range indicated in Table 5represents the two example rate values assessed. The lower flow rate maybe performed for Runs 1-4, and the higher flow rate may be performed forRun 5.

The elapsed times required to perform the protocol described in Table 5are shown in Table 6.

TABLE 6 Approximate, non-optimized elapsed times required to perform the⁹⁰Y isolation and purification process. ^(a) Runs 1-4 Run 5 ElapsedCumulative Elapsed Cumulative time, time, time, time, Step Descriptionmin min min min 1 C1 17 17 19 19 2 C2 3 ⁹⁰Y load/wash 22 39 15 34 4 ⁹⁰Ytransfer 26 65 14 48 5 Wash 9 74 6 54 6 ⁹⁰Y elute 30 104 7 61 7 Clean-up^(b) 20 124 20 81 ^(a) Indicated times include line blow-outs at eachstep and manual fraction collection activities (which introduced someadditional time). ^(b) Approximate values; elapsed times not closelytracked.

An example product solution, which had a ⁹⁰Sr activity concentration of1.25 Ci/mL, contained the stable Group II element concentrations listedin the 2nd column of Table 7 for Ca, Sr, and Ba. The Y concentration wasbased on the approximate mass concentration of ⁹⁰Y present in a ⁹⁰Srsolution of this activity concentration. The element and activityconcentrations in Table 7 are but one example of a ⁹⁰Sr productcomposition, and may not be representative of other ⁹⁰Sr batches.

TABLE 7 Stable elements added to ⁹⁰Sr-spiked simulated working stock,considering a target ⁹⁰Sr activity concentration of 1.25 Ci/mL. SumGroup II Group Est. Mass Elements, II: Y Ele- conc., in 6 mL, μmolesμmoles mole ment μg/mL μg ^(b) in 6 mL in 6 mL ratio Ca 540 3240 80.84 Sr     50,250 ^(a) 301,500 3441 ^(a)     Ba  20 120 0.874 3523 22,980 Y   2.30 ^(c) 13.80 0.153 ^(a) Sr mass concentration includescontributions from ⁹⁰Sr. ^(b) Per 7.5 Ci of example ^(c) Based on ⁹⁰Yspecific activity and activity concentration of 1.25 Ci/mL.

Given the example 1.25 Ci/mL ⁹⁰Sr activity concentration, it wasapproximated that 6.4 mL of this solution would be required to obtain asynthetic 8 Ci ⁹⁰Sr solution. A 6.0 mL sample injection loop can beinstalled in system 60 (“SL”, FIG. 6), which can allow for routinelyinjecting a simulated ⁹⁰Sr solution, the salt content of which would beequivalent to ˜7.5 Ci ⁹⁰Sr. Based on this 6.0 mL injection, the total μg(and μmoles) of the Group II elements are listed in Table 7.

⁹⁰Sr/⁹⁰Y-bearing solutions that closely simulated the elementalcomposition of a stock Sr bearing solution was prepared. The solutionstable element compositions are listed in Tables 1 and 7 and the spiked⁹⁰Sr activity values are listed in Table 2.

The isolated ⁹⁰Y produced by this (or any) purification method formedical purposes oftentimes requires a ⁹⁰Y: ⁹⁰Sr activity ratio of≥1×10⁶:1. Accordingly, for every 1 Ci ⁹⁰Y in an isotope product, amaximum of 1×10⁻⁶ Ci (1 μCi)⁹⁰Sr may be allowable. Based on the molarspecific activities in Table 8, 1 μCi ⁹⁰Sr is equivalent to 4.7×10⁻⁴μmoles (0.47 nmoles) of Group II elements (see, for example, simulated⁹⁰Sr stock solution that is described in Table 7).

TABLE 8 Molar specific activity calculations for pure ⁹⁰Sr and ⁹⁰Y, aswell as ⁹⁰Sr + Group II elements in simulated aged ⁹⁰Sr stock. Specificactivity Specific activity (pure radionuclide) (w/all Group II elements)Radionuclide μg/Ci μmoles/Ci μmoles/Ci ⁹⁰Sr 7.28 × 10³ 8.30 × 10¹  4.70× 10² ^(a) ⁹⁰Y 1.84 × 10⁰ 2.04 × 10⁻² ^(a) 3523 μmoles/7.5 Ci of ⁹⁰Sr(per Table 7).

Using the ⁹⁰Y isolation and purification processes of the presentdisclosure, at least a 10⁶-fold activity enrichment of ⁹⁰Y over ⁹⁰Sr maybe attainable. Based on the starting ⁹⁰Sr activity levels present in thefive test runs (1-5), the maximum ⁹⁰Sr activity levels in the ⁹⁰Yproduct fractions are shown in Table 9.

TABLE 9 ⁹⁰Sr activities that were spiked into each column load solutionprior to ⁹⁰Y purification (as replicated in Table 2), and the requiredmaximum ⁹⁰Sr activity levels in the ⁹⁰Y product fraction to achieve a10⁶-fold ⁹⁰Y activity enrichment factor. Determined ⁹⁰Sr Max. ⁹⁰Sractivity activity, after ⁹⁰Y purification, Run Run date μCi ^(a) μCi^(b) 1 Feb. 15, 2019 3.96E+2 3.96E−4 (2.12E+0) 2 Feb. 20, 2019 7.41E+27.41E−4 (2.12E+0) 3 Feb. 21, 2019 7.66E+2 7.66E−4 (1.56E+0) 4 Feb. 26,2019 6.82E+2 6.82E−4 (8.85E−1) 5 Feb. 27, 2019 7.02E+2 7.02E−4 (5.05E−1)^(a) Mean and (±1 s) values obtained from replicate measurements takenthroughout the study interval. ^(b) Maximum ⁹⁰Sr activity after a 10⁶⁹⁰Y product enrichment factor.

The ⁹⁰Y isolation and purification method (Table 5) can be performedusing the system 60 shown in FIG. 6. The process can be performed fivetimes, with ⁹⁰Sr solution injections containing elevated Ca, Sr, Ba, andY levels to simulate the levels in ˜7.5 Ci of an example 90Sr productsolution. ⁹⁰Sr activity levels in each of the five solutions ispresented in Table 9; these activities can be dissolved in 6 mL ofsolution, and can be injected into the fluidic system using a sampleinjection loop (SL, FIG. 6).

The tandem column process can include a Ln resin and a DGA resin column,respectively. Once the ⁹⁰Sr/⁹⁰Y solution is loaded into the sampleinjection loop, in semi-automated fashion, for example, with aperistaltic pump, the ⁹⁰Y isolation and purification process can befully automated.

For Run 1, which contained the least ⁹⁰Sr/⁹⁰Y activity of the five runs,a fraction collector can be employed to collect fractions of ˜2 mLvolume across the entire process (except for the ⁹⁰Y elution step,during which <1 mL fractions were collected). The ⁹⁰Y activitychromatogram is shown immediately after the conclusion of the run, andonce the samples achieved secular equilibrium (FIG. 7). The first three⁹⁰Y elution fractions, representing 0.85 mL, can contain 83% of the ⁹⁰Yin the injected sample.

When the ⁹⁰Sr in the fractions reach equilibrium with ⁹⁰Y, the profileof the unretained ⁹⁰Sr, traveling from the sample injection loop andthrough the load/wash of column 1 can be determined. Example fractionsshown can each be 2 mL in volume. The ⁹⁰Sr can be in the first 6 mLvolume; the next 2 mL fraction can contain the bulk of the residual⁹⁰Sr. This ˜30 μCi of ⁹⁰Sr may be carried from the sample injection loopas a segment of wash solution trapped between two air segments, forexample. With the passing of the air segments, the ⁹⁰Sr activity may beat baseline for the remainder of the column wash. Overall, 97% of the⁹⁰Sr in the load/wash fraction may be accounted for.

Runs 2 through 5 can contain approximately double the ⁹⁰Sr/⁹⁰Y activityof Run 1. Some fractions (the ⁹⁰Sr load effluent and the early ⁹⁰Yelution), can be split into two. For the ⁹⁰Sr load, the first and second10 mL fractions can be collected (except for Run 2, in which the first18.2 mL and the second 2.35 mL were collected). For the ⁹⁰Y elution, thefirst 0.72 to 0.84 mL can be collected in one fraction, and theremainder of the 2.5 mL ⁹⁰Y elution volume in the second fraction.

In FIG. 8 and with reference to Tables 11 and 14, for Run 2, the ⁹⁰Yyield can be determined in the primary elute fraction can be 95%; the⁹⁰Sr recovery in the equilibrated primary load fraction can be 98%. InFIG. 9, for Run 3, the ⁹⁰Y yield in the primary elute fraction can be86%; the ⁹⁰Sr recovery in the equilibrated primary load fraction can be97%. In FIG. 10, for Run 4, the ⁹⁰Y yield in the primary elute fractioncan be 86%; the ⁹⁰Sr recovery in the equilibrated primary load fractioncan be 100%. In FIG. 11, for Run 5, the ⁹⁰Y yield in the primary elutefraction can be 89%; the ⁹⁰Sr recovery in the equilibrated primary loadfraction can be 104%.

Additionally, a 2 μL aliquot of the Run 5 primary column load/washfraction effluent can be sampled immediately upon collection. Thealiquot can be added to scintillation cocktail and the resulting samplecounted by liquid scintillation analyzer (LSA). This sample can beperiodically counted until the sample approaches ⁹⁰Sr/⁹⁰Y secularequilibrium. The LSA pulse height spectra at time “near-zero” and beyondare shown in FIG. 12. The high-energy ⁹⁰Y β⁻ emission region is apparentabove the lower-energy ⁹⁰Sr β⁻ emission region beyond ˜1000 channels.The time “zero” spectra indicates virtually no ⁹⁰Y is present in thesample—it has been adsorbed onto the primary Ln Resin column. As timeprogresses, ⁹⁰Y ingrowth from the ⁹⁰Sr parent is observed.

Example performance of the tandem purification process is shown in Table10 for ⁹⁰Y. The table provides the total injected ⁹⁰Sr/⁹⁰Y into system60, and the determined ⁹⁰Y activity across all the collected fractions.Table 11 uses the Table 10 data to calculate the total ⁹⁰Y recoveryacross all fractions (% activity balance), and the ⁹⁰Y recovery in thecolumn 2 elution.

TABLE 10 Determined ⁹⁰Y activities (μCi) obtained immediately aftercompletion of the tandem column purification process, including fluidicsystem rinses and spent columns. Column 2 ⁹⁰Y elution activities are inbold. Run 1 Run 2 Run 3 Run 4 Run 5 Elapsed days ^(a) 0.087 0.050 0.0380.073 0.054 Units μCi Injected activity 3.96E+2 7.41E+2 7.66E+2 6.82E+27.02E+2 reference ^(b, c) (2.12E+0) (2.12E+0) (1.56E+0) (8.85E−1)(5.05E−1) C1 Load/Wash 2.19E+1 4.28E+1 3.82E+1 4.34E+1 3.80E+1 C1→C2Transfer 1.01E+1 2.65E+1 1.91E+1 2.41E+1 4.03E+1 C2 Wash 3.25E−3 7.69E−37.53E−3 3.33E−3 7.22E−2 C2 ⁹⁰ Y Elute 3.30E+2 7.01E+2 6.57E+2 5.89E+26.26E+2 System Rinses 1.76E+0 3.38E−1 2.03E−1 1.68E−1 1.57E+0 Col. 15.35E−2 3.94E−1 1.83E−2 3.18E−2 4.46E−2 Col. 2 3.76E−2 3.83E−1 1.10E−19.10E−2 9.27E−2 Sum of fractions ^(d) 3.64E+2 7.71E+2 7.15E+2 6.57E+27.06E+2 ^(a) Elapsed time at which activity fractions were calculated.^(b) Small aliquot of the original ⁹⁰Sr/⁹⁰Y column load solution,extrapolated to total load volume. ^(c) Mean and (±1 s) values obtainedfrom replicate measurements taken throughout the study interval. ^(d)Activity sum across all collected/analyzed column effluent fractions,system rinses, and spent columns.

Across all five runs, 97.2±5.0% of the activity injected into the systemcan be accounted for. This ±5.0% was assessed as the uncertainty in themeasurement approach. Consequently, this same relative uncertainty canbe used to assign uncertainties to the individual ⁹⁰Y elution yields.Across all five runs, it can be determined that the mean ⁹⁰Y elutionfraction was 87.8±4.3% of the total injected ⁹⁰Y. The ⁹⁰Y yields for Run5, which was performed at higher flow rates (for example doubled) thanRuns 1-4, can result in ⁹⁰Y product yields that can be statisticallyindistinguishable from the other runs.

The decay of each primary ⁹⁰Y elution fraction for the five runs can beperiodically monitored radiometrically. The activity of the initial ⁹⁰Ysample can be normalized at time near-zero to “1”, then calculate theactivity fraction across the next ˜60 days. The charts in FIG. 13through FIG. 17 show the decaying ⁹⁰Y elution fraction overlaid atop thetheoretical ⁹⁰Y decay rate. In all cases, the decaying ⁹⁰Y elutionfraction can remain atop the theoretical curve. Should any ⁹⁰Sr havebeen present in these ⁹⁰Y product fractions, the data would have begunto rise above the theoretical curve.

Upon approaching ˜60 elapsed days of counting, the ⁹⁰Y activity in the⁹⁰Y product fractions can became too low to accurately measure by theradiometric detector. At that point, some of the volume of the primary⁹⁰Y elution fractions may be sacrificed to inject into scintillationcocktail. The samples can then be counted across several more days byLSA. Because of the low activity levels, the samples may be counted forextended periods of time (2 h each) to obtain count rates, which maythen converted to net count rates and ultimately decay units (Bq).

The decay rates from the LSA samples described above can be converted todecay rates for each analysis date; ⁹⁰Y product fraction activity (Bq)results are displayed in FIG. 18. The elapsed time between the ⁹⁰Ypurification runs and the LSA analyses are shown in Table 12. As shownin FIG. 18, the decay rates for the samples continue to diminish overtime; this is indication that the primary source of activity in thesamples remains as ⁹⁰Y. As such, these decay rates should continue tofall until ⁹⁰Y achieves secular equilibrium with the trace levels of⁹⁰Sr present in the samples.

TABLE 12 Elapsed time between LSA count results shown in FIG. 17 andinitiation of the tandem column purification. Approx. elapsed days toLSA count Run ID Apr. 24, 2019 Apr. 29, 2019 May 2, 2019 1 68 73 76 2 6368 71 3 62 67 70 4 57 62 65 5 56 61 64

The LSA data in FIG. 18 can be used to calculate the ⁹⁰Srdecontamination factors in the primary ⁹⁰Y product fractions. Asactivity levels continue to drop in the LSA samples, the ⁹⁰Srdecontamination factors continue to rise with time, as shown in FIG. 19.

Stocks of ⁹⁰Sr bearing material can be considered a consumable item inthe described process; some losses of ⁹⁰Sr will be anticipated with each⁹⁰Y milking cycle. However, it is desirable to retain as much ⁹⁰Sr aspossible at the conclusion of the ⁹⁰Y separation process. High ⁹⁰Srrecoveries can be beneficial for at least two reasons: 1) unrecovered⁹⁰Sr will require additional purchases to replace losses in thestockpile, and 2) ⁹⁰Sr activity levels in process effluents andperipheral components will increase the cost of waste disposal.

Therefore, in addition to obtaining a high-purity ⁹⁰Y product with highyields, a method that would result in high recoveries of ⁹⁰Sr at theconclusion of each purification cycle would be beneficial. Ideally,virtually all of the ⁹⁰Sr would be recoverable in the effluents of theprimary ⁹⁰Y extraction column.

Activity results of fractions collected during the tandem columnpurification process (FIG. 7 through FIG. 11). Each figure presents thefractional activities near time “zero” (left-side), and near 50-60elapsed days (right-side) following the performance of the ⁹⁰Ypurification process. While the left-side figures provided fractional⁹⁰Y activities, the right-side figures provided fractional ⁹⁰Sractivities.

The distribution of ⁹⁰Sr recovered from all the dual-column effluentsand peripheral components involved in the tandem column purificationprocess are listed in Table 13. The top shaded row provides thedetermined spiked activity of ⁹⁰Sr injected into each of the five runs;they range between ˜400 and ˜770 μCi. The row in bold reports the ⁹⁰Sractivity recovered in the column 1 ⁹⁰Y load/wash effluents. The bottomshaded cell provides the sum of all ⁹⁰Sr accounted for during the tandemcolumn purification process.

TABLE 13 Determined ⁹⁰Sr activities (μCi) in each portion of the tandemcolumn purification process, including fluidic system rinses and spentcolumns. Recovered ⁹⁰Sr activity in Col. 1 load/wash is in bold. Run 1Run 2 Run 3 Run 4 Run 5 Elapsed days ^(a) 59.0 53.9 52.9 48.3 47.4 UnitsμCi Injected activity 3.96E+2 7.41E+2 7.66E+2 6.82E+2 7.02E+2 reference^(b, c) (2.12E+0) (2.12E+0) (1.56E+0) (8.85E−1) (5.05E−1) C1 Load/Wash3.84E+2 7.25E+2 7.45E+2 6.82E+2 7.34E+2 C1→C2 Transfer 3.93E−3 1.70E−22.31E−2 3.01E−4 1.73E−2 C2 Wash <MDA <MDA <MDA <MDA <MDA C2 ⁹⁰Y Elute<MDA 5.76E−4 7.35E−4 2.11E−3 2.78E−3 System Rinses 2.16E−1 7.81E−28.33E−2 8.43E−3 1.34E+0 Col. 1 1.90E−3 3.85E−3 3.89E−3 4.42E−3 1.23E−3Col. 2 <MDA <MDA <MDA 1.08E−5 <MDA Sum of fractions ^(d) 3.85E+2 7.25E+27.45E+2 6.82E+2 7.35E+2 ^(a) Elapsed time at which activity values wereobtained. ^(b) Small aliquot of the original ⁹⁰Sr/⁹⁰Y column loadsolution, extrapolated to total load volume. ^(c) Mean and (±1 s) valuesobtained from replicate measurements taken throughout the studyinterval. ^(d) Activity sum across all collected and analyzed columneffluent fractions, system rinses, and spent columns.

The data in Table 13 illustrates that virtually all of the ⁹⁰Sr activitywas accounted for in the column 1 load/wash fraction. The fractions withthe next-highest ⁹⁰Sr activities contained levels that were ≤1.8×10⁻³relative to the load/wash fraction (see “system rinses” in Run 5).

The data in Table 14 summarizes the ⁹⁰Sr yields across each of the fiveruns. First, the fraction of ⁹⁰Sr accounted for in the Table 13 “sum offractions” vs. the “injected activity reference” values. Overall, it canbe possible to account for 99.4±3.2% of the ⁹⁰Sr relative to thereference aliquots that may be sampled prior to initiating the ⁹⁰Ypurification process. The relative uncertainty of ±3.2% can be employedto assign uncertainties to the ⁹⁰Sr activities accounted for in the“column 1 load/wash” fraction. Based on this, a mean ⁹⁰Sr recovery of99.3±3.1% in the column 1 load/wash effluents across all five runs canbe obtained. Virtually all of the ⁹⁰Sr injected into the ⁹⁰Ypurification process may be recoverable in the fluids emerging from theprimary Ln Resin column.

In compliance with the statute, embodiments of the invention have beendescribed in language more or less specific as to structural andmethodical features. It is to be understood, however, that the entireinvention is not limited to the specific features and/or embodimentsshown and/or described, since the disclosed embodiments comprise formsof putting the invention into effect. The invention is, therefore,claimed in any of its forms or modifications within the proper scope ofthe appended claims appropriately interpreted in accordance with thedoctrine of equivalents.

1. A method for separating Y and Sr, the method comprising: providing adilute acidic mixture comprising Y and Sr to a first vessel having afirst media therein; and while providing the dilute acidic mixture,retaining at least some of the Y from the dilute acidic mixture withinthe first vessel while eluting at least some of the Sr from the diluteacidic mixture to form a dilute acidic eluent.
 2. The method of claim 1wherein the dilute acidic mixture comprises ⁹⁰Y and ⁹⁰Sr.
 3. The methodof claim 1 wherein the dilute acidic mixture additionally comprisesstable Sr, Ca and/or Ba.
 4. The method of claim 1 wherein the diluteacidic mixture comprises stockpiled Sr-bearing nuclear material.
 5. Themethod of claim 1 wherein the first media comprises a resin.
 6. Themethod of claim 1 wherein the first media comprises an HDEHP resin. 7.The method of claim 1 wherein the first media comprises alkylphosphorusextractants.
 8. The method of claim 1 wherein the dilute acidic eluentcomprises at least some Sr from the dilute acidic mixture.
 9. The methodof claim 1 further comprising: providing the dilute acidic mixture froma reservoir; and providing the dilute acidic eluent to the reservoir.10. The method of claim 1 wherein the dilute acidic mixture furthercomprises Zr.
 11. The method of claim 10 wherein while providing thedilute acidic mixture, further comprising retaining at least some of theZr from the dilute acidic mixture within the first vessel.
 12. Themethod of claim 1 wherein the dilute acidic mixture further comprisesFe.
 13. The method of claim 10 wherein while providing the dilute acidicmixture, further comprising retaining at least some of the Fe from thedilute acidic mixture within the first vessel.
 14. The method of claim 1wherein the dilute acidic mixture comprises HCl.
 15. A method forseparating Y and Sr, the method comprising: providing a first vesselcontaining a first media and dilute acidic mixture comprising Y;providing a concentrated acid mixture to the first vessel; and whileproviding the concentrated acid mixture to the first vessel, recoveringa concentrated acid eluent comprising at least some of the Y from withinthe first vessel.
 16. The method of claim 15 wherein the first mediacomprises a resin.
 17. The method of claim 15 wherein the first mediacomprises an HDEHP resin.
 18. The method of claim 15 wherein the firstmedia comprises alkylphosphorus extractants.
 19. The method of claim 15wherein the first vessel contains ⁹⁰Y.
 20. The method of claim 15wherein the first vessel contains one or both of Zr and Fe.
 21. Themethod of claim 20 wherein while providing the concentrated acid mixtureto the first vessel, retaining at least some of the one or both of theZr and Fe.
 22. The method of claim 15 wherein the concentrated acidmixture comprises HCl.
 23. The method of claim 15 further comprisingproviding the concentrated acid eluent to a second vessel containing asecond media.
 24. A method for separating Y and Sr, the methodcomprising: providing a concentrated acidic mixture comprising Y to avessel having a media therein; and while providing the concentratedacidic mixture, retaining at least some of the Y from the concentratedacidic mixture within the vessel and forming an eluent.
 25. The methodof claim 24 wherein the concentrated acidic mixture comprises ⁹⁰Y. 26.The method of claim 24 wherein the media comprises a resin.
 27. Themethod of claim 24 wherein the media comprises a diglycolamide resin.28. The method of claim 24 wherein the media comprises N, N, N′,N′-tetra-n-octyldiglycolamide.
 29. The method of claim 24 wherein theconcentrated acidic mixture comprises at least some Sr.
 30. The methodof claim 29 wherein while providing the concentrated acidic mixture,retaining at least some of the Y from the concentrated acidic mixturewithin the vessel and forming an eluent comprising at least some of theSr.
 31. The method of claim 24 wherein the concentrated acidic mixturecomprises at least some Zr.
 32. The method of claim 31 wherein whileproviding the concentrated acidic mixture, retaining at least some ofthe Zr from the concentrated acidic mixture within the vessel.
 33. Themethod of claim 24 wherein the concentrated acidic mixture comprises atleast some Fe.
 34. The method of claim 33 wherein while providing theconcentrated acidic mixture, retaining at least some of the Fe from theconcentrated acidic mixture within the vessel.
 35. A method forseparating Y and Sr, the method comprising: providing a vesselcontaining a media and a concentrated acidic mixture comprising Y;providing a dilute acid mixture to the vessel; and while providing thedilute acid mixture to the vessel, recovering a dilute acid eluentcomprising at least some of the Y from within the vessel.
 36. The methodof claim 35 wherein the media comprises a resin.
 37. The method of claim35 wherein the media comprises a diglycolamide resin.
 38. The method ofclaim 35 wherein the media comprises N, N, N′,N′-tetra-n-octyldiglycolamide.
 39. The method of claim 35 wherein thevessel contains ⁹⁰Y.
 40. The method of claim 35 wherein the vesselcontains one or both of Zr and Fe.
 41. The method of claim 40 whereinwhile providing the diluted acid mixture to the vessel, eluting at leastsome of the one or both of the Zr and/or Fe.
 42. The method of claim 35wherein the diluted acid mixture comprises HCl.
 43. The method of claim35 wherein the vessel contains Sr.
 44. The method of claim 40 whereinwhile providing the diluted acid mixture to the vessel, eluting at leastsome of the Sr.
 45. A method for separating Y and Sr, the methodcomprising: providing a dilute acidic mixture comprising Y and Sr to afirst vessel having a first media therein; separating at least some ofthe Sr from the Y of the dilute acidic mixture; eluting at least some ofthe Y from first vessel to form a concentrated acid eluent comprising Y;providing the concentrated acid eluent to a second vessel having asecond media therein; and eluting at least some of the Y from the secondvessel to form a dilute acid eluant comprising Y.
 46. The method ofclaim 45 wherein the dilute acidic mixture comprises ⁹⁰Y and ⁹⁰Sr. 47.The method of claim 45 wherein the dilute acidic mixture additionallycomprises stable Sr, Ca and/or Ba.
 48. The method of claim 45 whereinthe dilute acidic mixture comprises stockpiled Sr-bearing nuclearmaterial.
 49. The method of claim 45 wherein the first media comprises aresin.
 50. The method of claim 45 wherein the first media comprises anHDEHP resin.
 51. The method of claim 45 wherein the first mediacomprises alkylphosphorus extractants.
 52. The method of claim 45further comprising: providing the dilute acidic mixture from areservoir; and wherein the separating comprises recovering a diluteacidic eluent comprising Sr, and providing the dilute acidic eluentcomprising Sr to the reservoir.
 53. The method of claim 45 wherein thedilute acidic mixture further comprises Zr.
 54. The method of claim 53wherein while providing the dilute acidic mixture, further comprisingretaining at least some of the Zr from the dilute acidic mixture withinthe first vessel.
 55. The method of claim 45 wherein the dilute acidicmixture further comprises Fe.
 56. The method of claim 55 wherein whileproviding the dilute acidic mixture, further comprises retaining atleast some of the Fe from the dilute acidic mixture within the firstvessel.
 57. The method of claim 45 wherein the dilute acidic mixturecomprises HCl.
 58. The method of claim 45 wherein the first vesselcontains ⁹⁰Y.
 59. The method of claim 45 wherein the first vesselcontains one or both of Zr and Fe.
 60. The method of claim 59 whereinwhile providing the concentrated acid mixture to the first vessel,retaining at least some of the one or both of the Zr and Fe.
 61. Themethod of claim 45 wherein the second media comprises a resin.
 62. Themethod of claim 45 wherein the second media comprises a diglycolamideresin.
 63. The method of claim 45 wherein the second media comprises N,N, N′, N′-tetra-n-octyldiglycolamide.
 64. The method of claim 45 whereinthe diluted acid mixture comprises HCl.
 65. A method for separating Yand Sr, the method comprising: providing a strong acidic mixturecomprising Y and Sr to a first vessel having a first media therein;separating at least some of the Sr from the Y of the strong acidicmixture; eluting at least some of the Y from first vessel to form adilute acid eluent comprising Y; providing the dilute acid eluent to asecond vessel having a second media therein; and eluting at least someof the Y from the second vessel to form a concentrated acid eluantcomprising Y.
 66. The method of claim 65 wherein the strong acidicmixture comprises ⁹⁰Y and ⁹⁰Sr.
 67. The method of claim 65 wherein thefirst media comprises a resin.
 68. The method of claim 65 wherein thefirst media comprises a diglycolamide resin.
 69. The method of claim 65wherein the first media comprises N, N, N′,N′-tetra-n-octyldiglycolamide.
 70. The method of claim 65 wherein thedilute acidic eluent comprises HCl.
 71. The method of claim 65 whereinthe first vessel contains ⁹⁰Y.
 72. The method of claim 65 wherein thesecond media comprises a resin.
 73. The method of claim 65 wherein thesecond media comprises an HDEHP resin.
 74. The method of claim 65wherein the second media comprises alkylphosphorus extractants.
 75. Themethod of claim 65 wherein the concentrated acid eluent comprises HCl.76. A method for separating Y and Sr, the method comprising: providing afirst mixture of Y and Sr to a first vessel having a first volume;separating at least some of the Y from the first mixture to form asecond mixture comprising the separated Y and transferring the secondmixture to a second vessel having a second volume, wherein the firstvolume is greater than or equal to the second volume; and transferringat least some of the separated Y from the second vessel to form a thirdmixture comprising the transferred Y, wherein the Y concentration of thefirst mixture is less than the Y concentration of the third mixture. 77.The method of claim 76 wherein the first and third mixtures are diluteacid mixtures.
 78. The method of claim 77 wherein the acid mixturescomprise HCl.
 79. The method of claim 76 wherein the first vessel housesa first media and the second vessel houses a second media.
 80. Themethod of claim 76 wherein the first media is chemically different thanthe second media.
 81. The method of claim 76 wherein the second mixtureis a concentrated acid mixture.